Product Overview
G10 and FR4 tubes are epoxy fiberglass laminate tubes used for electrical insulation and structural applications. Produced from woven glass cloth and epoxy resin, then CNC-machined to final dimensions, these tubes combine high dielectric strength, mechanical rigidity, and dimensional stability — the tubular counterpart of the G10/FR4 sheet family.
Because every tube is finished by machining, inner diameter, outer diameter, wall thickness, and length are not limited to catalog sizes. Slots, holes, threads, and stepped profiles can be added in the same setup, so a single tube can serve as an insulating bushing, coil form, spacer sleeve, or structural sleeve without secondary assembly.
Available in G10, FR4, and G11 grades, epoxy glass tubes meet the NEMA laminate family standards (see the G10 material guide for grade definitions and NEMA / IEC EPGC / 3240 equivalents). They are widely used by electrical utilities, switchgear builders, transformer OEMs, and industrial equipment manufacturers.
Technical Properties & Performance Data
Electrical Properties
| Property | Test Method | G10 | FR4 | G11 | Units |
|---|---|---|---|---|---|
| Dielectric Strength (perpendicular) | ASTM D149 | 16-20 | 18-22 | 17-21 | kV/mm |
| Dielectric Constant @ 1MHz | ASTM D150 | 4.5-5.5 | 4.4-5.2 | 4.6-5.4 | – |
| Volume Resistivity | ASTM D257 | >10¹⁴ | >10¹⁴ | >10¹⁴ | Ω·cm |
Mechanical & Thermal Properties
| Property | G10 | FR4 | G11 | Units |
|---|---|---|---|---|
| Tensile Strength | 275-345 | 275-345 | 275-345 | MPa |
| Flexural Strength | 415-480 | 415-480 | 415-480 | MPa |
| Compressive Strength | 415-550 | 415-550 | 415-550 | MPa |
| Continuous-Use Temperature | ~130 | ~130 | ~155-180 | °C |
| Flame Rating | Not rated | UL94 V-0 class | Not rated | – |
| Water Absorption (24 h) | 0.10-0.15 | 0.10-0.15 | 0.10-0.15 | % |
Values are typical published ranges; actual performance varies by manufacturer, wall construction, and test direction. Request the material datasheet for the specific lot when the application is governed by a standard or safety code.
Sizes, Tolerances & Machining
- Diameter range: custom ID/OD per drawing — from small instrument bushings (a few millimeters ID) to large insulating sleeves; confirm availability for very large diameters at quote stage
- Wall thickness: per drawing; thin-wall sleeves and heavy-wall structural tubes both machinable
- Length: cut to specification, from short spacer sleeves to full-length tubes
- Tolerances: ±0.1–0.3 mm typical on machined diameters; tighter tolerances quoted on request
- Secondary machining: slots, cross-holes, internal/external threads (coarse; inserts recommended for repeated assembly), stepped ends, and chamfers
- Finish: natural laminate color, deburred edges, free of delamination
Carbide or diamond tooling is used throughout — the woven glass reinforcement is abrasive and wears high-speed steel quickly. For process detail see G10 & FR4 machined parts.
Typical Applications
- Insulating bushings and sleeves for bolts, shafts, and conductors passing through grounded panels
- Coil forms and winding forms for transformers, inductors, and motors
- Spacer sleeves and standoff tubes maintaining fixed spacing in busbar, switchgear, and chassis assemblies
- Structural insulating members where a non-conductive tube carries mechanical load
- High-temperature fixtures (G11 grade) near motors, transformers, and power electronics
Pair with custom insulating washers for complete bolt-isolation kits, or with the epoxy glass composite rod for matching solid-round components.
Frequently Asked Questions
What sizes of G10 tube can you supply?
Tubes are machined to drawing rather than picked from a catalog, so ID, OD, wall thickness, and length can all be customized. Send the drawing or required dimensions for confirmation of stock and lead time.
What is the difference between a G10 tube and an FR4 tube?
Same base laminate family; FR4 adds flame-retardant chemistry (UL94 V-0 class). Choose FR4 when a flame rating is specified, G10 when it is not. For service above 130 °C, choose G11.
Can G10 tubes be threaded or slotted?
Yes. Tubes can be drilled, slotted, chamfered, and tapped for coarse threads. For repeated assembly, thread inserts are recommended over direct-tapped laminate.
Is a G10 tube electrically insulating?
Yes. Like the sheet family, G10/FR4 tube is a non-conductive electrical insulator with typical dielectric strength in the 16–22 kV/mm range (perpendicular, per ASTM D149). Keep surfaces clean and dry for high-voltage service.
Do you also supply G10 rod and sheet parts?
Yes — solid rod via the epoxy glass composite rod page, and flat machined parts (washers, spacers, panels) via G10 & FR4 machined parts. We do not sell raw laminate sheet.
What do you need for a quote?
Grade (G10/FR4/G11), ID × OD × length, wall tolerance, quantity, secondary machining (slots/holes/threads), and the operating environment (voltage, temperature, moisture). Submit through the quote request page for a 24-hour response.
Request a Quote for G10/FR4 Tubes
Send your drawing or dimensions through the quote request page. A quotation with material datasheet support is returned within 24 hours; prototypes can be machined for validation before production quantities.
